They're both covered in fur, walk on four legs, have whiskers and expressive tails -- how different can your dog and cat possibly be? When it comes to nutrition and feeding, the answer is very different. Though there's no harm if your pup snags a bit of your cat's food, it's not healthy for him to eat cat food in the long run.
Cat Versus Dog Nutrition
You wouldn't consider your dog's diet appropriate for your best health because you're of a different species than him. The same is true for cats and dogs: They're two entirely different species with distinct nutritional needs. The Association of American Feed Control Officials establishes feeding guidelines for cats and dogs based on their unique nutritional needs.
According to AAFCO's standards, a dog's diet should be comprised of between 18 and 22 percent protein, compared to 26 to 30 percent for a cat. A cat is an obligate carnivore, meaning her protein should come from animal-based sources. Animal meat provides a cat the amino acids she needs for her good health -- particularly taurine, a vital amino acid found only in animal protein. One of the other many differences between cat and dog dietary requirements and food is fat content. Cat food tends to have a higher fat content; fats are not only a good source of energy for a cat, but provide fatty acids and help absorb fat-soluble vitamins.
Risk of Obesity
Given cat food's extra protein and fat content, it's little wonder your dog might prefer the cat's food to his. If your dog makes a habit of sneaking into the cat's food he's likely going to pack on some extra weight. You may not think an extra pound here or there will make a difference, but PetMD notes that even an extra couple of pounds can make a difference. Carrying extra weight can lead to a host of problems, including difficulty breathing, decreased stamina, high blood pressure, joint problems, diabetes, decreased immune system function, heat intolerance and liver disease.
Another potential problem of eating cat food is the chance of gastrointestinal upset. If your dog sneaks into a bag of cat food and has his way with it, it likely won't kill him, but he may not feel well. The higher protein and fat content of cat food can wreak havoc on the canine gastrointestinal tract, potentially resulting in diarrhea or vomiting. For the dog with a particularly sensitive tract, a steady diet or a binge of cat food may result in pancreatitis, which can be dangerous.
Separate but Equal
Your cat's unique nutritional needs cannot be met with dog food, and while your dog can survive on cat food, he will not thrive and may get sick and become overweight. If your pets are sampling and sharing from each other's food bowls, feed them at separate times, at separate locations. Don't forget the one thing they can share: plenty of fresh water, accessible to your dog and cat anytime.